(a) Field of the Invention
The present invention relates to an image analysis system and method of a biochip. More specifically, the present invention relates to an image analysis system and method for detecting an edge of a cDNA (complementary deoxyribonucleic acid) chip.
(b) Description of the Related Art
Biochips include glass or nylon membranes designed for accelerating genetic research, they are designed for providing a plurality of short DNA strands and essential genetic information for determining living creatures' characteristics on a single substrate, and they are frequently used as test tubes for chemical samples.
Biochips may accelerate checking of about 30,000 genes in human DNA, and progression of global coordinated research thereof, the so-called human genome project, for making a human genome map.
Biochips are classified into protein chips, oligonucleotide chips, and cDNA chips.
Regarding the protein chips, dozens to hundreds of different proteins or ligands are provided on the chip surface in a micro-array format. In this instance, when a sample is added to the protein chip, biomolecules specifically interactive with the proteins or ligands provided on the chip surface remain, and others are washed away.
Existence states or functions of the above interactive biomolecules are analyzed using an SPR (surface plasmon resonance) device, a mass spectrometer, or a fluorescence spectrometer. The protein chips may be effectively applied to cancers, AIDS (acquired immune deficiency syndrome), early diagnosis of human diseases, causal examination of diseases, and understanding of in vivo signal transduction systems.
Oligonucleotide chips use 25 oligonucleotides to search for mutations of specified genes. That is, oligonucleotide chips adopt a photolithography method to synthesize the oligonucleotides of a desired nucleotide sequence on a slide glass, and they search for mutations of tumor suppressive genes such as p53 and BRCA1 using the synthesized oligonucleotides.
Oligonucleotide chips may be applied to inherited disorder fields including gene mutation detection, drug resistance detection diagnosis, SNP (single nucleotide polymorphism) analysis, histocompatibility and organ transplantation assays, identification of pathogenic microorganisms, nucleotide sequence analysis, paternity tests, interracial polymorphism analysis, and forensic medicine.
As for cDNA chips, thousands to tens of thousands of genes are formed as 150 μm-sized spots on a predetermined slide glass substrate to create a cDNA micro-array, fluorescent labeling is performed on RNAs (ribonucleic acids) of two groups to be compared, that is, the RNA of a control group and that of an experimental group, and they are competitively combined to the DNA chip so as to check relative gene expression patterns.
The cDNA chips may be used for high throughput gene expression—analysis, human disease diagnosis and monitoring, biological response studies of environmental factors, food inspection, new drug development, clinicopathology, and for animal and plant quarantine.
A method for manufacturing cDNA chips will now be described.
Test genes are planted on a glass slide to thereby generate a cDNA micro-array chip having thousands of test genes. A cDNA micro-array chip generated in this manner contributes greatly to analysis of particular genes expressed in two different environments.
Messenger RNA (referred to as mRNA hereinafter) is extracted from cells obtained from the two different environments, and bases having fluorescence of different colors are provided to the mRNAs when the mRNAs are reverse-transcribed, thereby synthesizing red (Cy5) or green (Cy3) cDNAs or tagging the mRNAs.
In this instance, genes expressed in yellow are provided by a complementary color of green and red, and it is found that similar amounts of the above-noted genes are expressed under the two environments.
The two synthesized cDNAs or mRNAs as described above are mixed at a predetermined identical amount to thus combine them on a single cDNA micro-array chip, and when uncombined genes are washed from the chip, the chip is read by a laser fluorescent scanner. Fluorescence degrees of the respective genes represent the genes' expression degrees, and the degrees are analyzed by a computer.
When analyzing gene information, since the cDNA micro-array chip has cDNA of different genes formed as spots of about 100 μm diameter and printed on a glass slide or nylon fabric, the respective spots are separated into segments so as to measure expression degrees of the respective genes.
In this instance, a reference circle of a predetermined size is injected on the center of the segment so as to extract an effective spot, and if the size of the reference circle is greater than that of the spot, the background as well as the spot are positioned in the reference circle, and accordingly, errors occur in data mean values.
In another case, when the center of the spot is not located on the center of the segment but it digresses to a side, since the positions of the reference circle and the spot are not matched, a portion of the spot located in the reference circle is used as effective information, and the remaining spot area outside the reference circle is processed as a background to thereby increase data error rates.
In order to correct the errors generated from the above-described method, the intensity in the segment is represented in a histogram format, predetermined amounts of data values provided on the top and bottom portions of the histogram are discarded, and remaining data values are taken as effective information. In this case, effective data values may be problematically discarded even when correct data are extracted.